Captured mice being displayed at the cropland in Yueyang of central China's Hunan Province. Photograph: Long Hongtao/AP

The business management philosophy that one person's crisis is another's opportunity may perhaps never have been taken to such bizarre extremes.

A plague of 2 billion mice in central China was described just days ago as being so bad that it resembled a scene from a horror movie with roads and hillsides turned black with rodents.

But in a remarkable display of entrepreneurship, businessmen are catching, shipping and selling the eastern field mice, also known locally as rats, to the southern city of Guangzhou, where restaurants are reportedly offering rodent banquets to diners notorious for their unusual tastes.

"Recently there have been a lot of rats ... Guangzhou people are rich and like to eat exotic things, so business is very good," the China News Service quoted a vendor as saying.

According to Beijing News, businessmen from Guangzhou - the provincial capital of Guangdong - were offering 6 yuan (40 pence) for a kilogramme of live rodents.

The infestation was caused by some of the worst flooding in 50 years in central China. In the past two weeks, more than 400 people have died, 105 are missing and more than 3 million have been forced to evacuate their homes as a result of the deluge.

To ease pressure on rivers and plains, the giant Three Gorges dam released water to Dongting Lake in Hunan Province. After months of drought, the area was suddenly flooded, driving countless millions of rodents from their mouse holes.

Local villagers described their migration in terms of an army on the move, eating everything in their path. Entire crop fields were reportedly devoured in a single afternoon.

According to domestic media, the munching was so loud that it could be heard inside villagers' homes.

In the ensuing war on rodents, local people beat hundreds of mice to death. Some used ferrets, others so much poison that more than 1,000 cats and chickens were also killed.

The Xinhua news agency reported that more than 2 million rodents have been killed. Their bodies - weighing an estimated 90 tonnes in total - have been bagged, buried and covered with lime to prevent them spreading disease.

Although the infestation is reportedly the worst in 10 years, it is an annual occurrence during flood season.

Hunan province is attempting to raise more than 6m yuan (£400,000) to build a 24-mile wall to prevent future mice invasions.

Zoologists and hydrologists say the situation has been made worse by the depletion of predators and the increase of dams. The populations of snakes and owls - which eat mice - have decreased because they are popular dishes. The proliferation of dams has lessened the downstream waterflow, widening the habitable territory of the rodents.

Shi Dazhao, director of the Chinese Agricultural University's laboratory on the prevention and control of rodents, told the China Daily that the magnitude of this year's problem could be attributed to the Three Gorges dam and global warming.

Local people said the infestation was so bad that they could make a small fortune from selling "rats" to restaurants, but some baulked at the trade.

"If we want to do that, there is no problem," an unnamed villager told the Beijing news. "We could catch 150kg of rats in one night ... but we will not do this against our conscience".